The present invention relates to improvements in apparatus for opening or spreading folded sheets which consist of paper or the like. More particularly, the invention relates to improvements in apparatus for opening folded sheets in the form of signatures or the like, namely, groups of panels or layers having two sets of layers which are pivotable relative to each other along an edge portion of the multi-layer sheet, e.g., along the back of a signature.
It is already known to open folded multi-layer sheets of the above outlined character by resorting to a substantially horizontal transporting device which engages the edge portions of the folded sheets and advances the thus engaged sheets in an orientation such that the layers extend downwardly, i.e., that the layers can be spread apart or opened up by pivoting along the edge portion which is engaged and held by the transporting device. German Pat. No. 581,077 discloses an apparatus which embodies the just discussed transporting device and further employs suction generating elements alternating with retaining or spreading elements. The suction generating elements which are used in the apparatus of the German patent are small pipes which diverge from the path of the folded sheets as considered in the direction of travel of such sheets. One end portion of each pipe is immediately adjacent to the path of movement of folded sheets and the other end portion of each pipe is located behind the next-following retaining element. Each pipe has a plurality of suction ports. A drawback of the patented apparatus is that it can only be used for opening or spreading of folded sheets whose layers are relatively rigid, and also that the number of folded sheets which can be opened per unit of time is low so that the patented apparatus cannot be used in modern high-speed bookbinding, newspaper gathering or analogous machines.
German Pat. No. 1,945,501 discloses a modified apparatus for the opening of folded sheets which employs rotary suction generating elements disposed in pairs and at a level above the path of folded sheets. The layers are held in horizontal planes and spaced-apart portions of each layer are engaged and attracted by a pair of suction generating elements. The just discussed apparatus is bulky, complex and expensive.